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. 2022 Jan:114:21-28.
doi: 10.1016/j.ijid.2021.10.010. Epub 2021 Oct 12.

Protective Immunity after Natural Infection with Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) - Kentucky, USA, 2020

Affiliations

Protective Immunity after Natural Infection with Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) - Kentucky, USA, 2020

Kevin B Spicer et al. Int J Infect Dis. 2022 Jan.

Abstract

Background: As vaccine supply and access remain limited in many parts of the world, understanding the duration of protection from reinfection after natural infection is important.

Methods: Distinct individuals testing positive and negative for SARS-CoV-2 between March 6, 2020, and August 31, 2020, in Kentucky, USA, were identified using the Kentucky National Electronic Disease Surveillance System. Individuals were followed for occurrence of a positive test for SARS-CoV-2 from 91 days after their initial test result through December 31, 2020. Protection from reinfection provided by a prior infection was calculated and additional analyses evaluated impact of age, sex, symptom status, long-term care facility connection, testing occurrence and frequency, and time from initial infection.

Results: The protective effect from prior infection was 80.3% (95% CI, 78.2%-82.2%) for those aged 20-59 years and 67.4% (95% CI, 62.8%-71.4%) for those aged ≥60 years. At 30-day time periods through 270 days (with limited exceptions), protection was estimated to be >75% for those aged 20-59 years and >65% for those aged ≥60 years. Factors associated with repeat positive testing included a connection to a long-term care facility, duration of potential exposure, and absence of symptoms during initial infection.

Conclusions: Natural infection provides substantial and persistent immunologic protection for a period of several months for most individuals, although subpopulations may be at greater risk of repeat positive testing and potential poor outcomes associated with reinfection. These subgroups include individuals aged ≥60 years, residents and staff of long-term care facilities, and those who have mild or asymptomatic illness with initial infection. Continued emphasis on vaccination and infection prevention and control strategies remains critically important in reducing the risk of reinfection and associated severe outcomes for these groups.

Keywords: COVID-19; COVID-19 risk factors for reinfection; SARS-CoV-2; protective immunity after natural infection; reinfection.

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Figures

Figure 1
Figure 1
Event (positive test)-free survival for those with and without history of SARS-CoV-2 infection, by younger (ages 20–59) and older (60 years and older) age groups, June–December, 2020, Kentucky, USA
Figure 2
Figure 2
Percentage of group (initial negative test versus initial positive test) with specified number of tests performed >90 days after an initial qualifying test result, June–December, 2020, Kentucky, USA

References

    1. Armstrong JN, Campbell L, Tabatsky-her T, Leung V, Parikh S. Repeat positive SARS-CoV-2 RNA testing in nursing home residents during the initial 9 months of the COVID-19 pandemic: an observational retrospective analysis. The Lancet Regional Health – Americas. 2021 doi: 10.1016/j.lana.2021.100054. - DOI - PMC - PubMed
    1. Bajaj V, Gadi N, Spihlman AP, Wu SC, Choi CH, Moulton VR. Aging, immunity, and COVID-19: how age influences the host immune response to coronavirus infections. Front Physiol. 2021;11 doi: 10.3389/fphys.2020.571416. doi: - DOI - PMC - PubMed
    1. Breathnach DAS, Riley PA, Cotter MP, Houston AC, Habibi MS, Planche TB. Prior COVID-19 significantly reduces the risk of subsequent infection, but reinfections are seen after eight months. J Infect. 2021;82:e11–e12. doi: 10.1016/j.jinf.2021.01.005. - DOI - PMC - PubMed
    1. Canaday DH, Carias L, Oyebanji OA, Keresztesy D, Wilk D, Payne M, et al. Reduced BNT162b2 mRNA vaccine response in SARS-CoV-2-naïve nursing home residents. Clin Infect Dis. 2021 doi: 10.1093/cid/ciab447. - DOI - PMC - PubMed
    1. Carsetti R, Zaffina S, Mortari EP, Terreri S, Corrente F, Capponi C, et al. Different innate and adaptive immune responses to SARS-CoV-2 infection of asymptomatic, mild, and severe cases. Front Immunol. 2020 doi: 10.3389/fimmu.2020.610300. - DOI - PMC - PubMed

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